We have a website hosted in IIS 7.5, and we're trying to generate sitemap.xml sitemap_images.xml, but the application throws an error: "Error writing to these files: C:\..\sitemap.xml and C:\...\sitemap_images.xml. Please correct files permissions and resume sitemap creation".

We assigned permissions to IIS_IUSRS user on these files.Is this the user you have to assign permissions, or another user?